Stabilized acidic hydrogen peroxide solutions

ABSTRACT

Stabilizers are provided which control copper ion-catalyzed degradation of hydrogen peroxide. In pickling baths the H2O2 concentration may be up to about 50% by weight, in the presence of strong inorganic nonoxidizing acids at up to about 50% by weight, and at temperatures of up to about 90*C. Such stabilizers are included in concentrations of up to about 1.5% by weight. The stabilizers, at concentrations of up to about 5% by weight, may also be formulated into H2O2 of up to 80% concentration by weight. The stabilizers are selected from the group consisting of adipic acid, glutaric acid, succinic acid, their methyl derivatives, salts, and mixtures of them.

nited States Patent [191 Stalter Feb. 4, 1975 STABILIZED ACIDIC HYDROGEN PEROXIDE SOLUTIONS Neil J. Stalter, Wilmington, Del.

Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.

Filed: Dec. 4, 1972 Appl. No.: 311,976

Inventor:

FOREIGN PATENTS OR APPLICATIONS 1,041,586 9/1966 Great Britain 423/584 Primary Examiner-Richard D. Lovering Assistant Examiner-Irwin Gluck [57] ABSTRACT Stabilizers are provided which control copper ioncatalyzed degradation of hydrogen peroxide. In pickling baths the H O concentration may be up to about 50% by weight, in the presence of strong inorganic nonoxidizing acids at up to about 50% by weight, and at temperatures of up to about 90C. Such stabilizers are included in concentrations of up to about 1.5% by weight. The stabilizers, at concentrations of up to about 5% by weight, may also be formulated into H 0 of up to 80% concentration by weight. The stabilizers are selected from the group consisting of adipic acid, glutaric acid, succinic acid, their methyl derivatives, salts, and mixtures of them.

23 Claims, No Drawings STABILIZED ACIDIC HYDROGEN PEROXIDE SOLUTIONS BACKGROUND OF THE INVENTION Articles of copper or copper alloys are generally cleaned in an operation known as pickling by treatment with a mineral acid solution containing an oxidizing agent. The function of the oxidizing agent is to oxidize cuprous oxide scale and smut to the cupric form, in which valence state it is soluble in the pickling acid, usually sulfuric acid. The oxidizing agent commonly used has been sodium dichromate. However, because of the unacceptability of that chemical from the pollution standpoint, hydrogen peroxide is finding acceptance as the oxidizer.

It is well known, however, that copper ions catalyze the decomposition of hydrogen peroxide in acid medium, particularly at the elevated temperatures used for pickling baths. Thus, there has been a continuing search for materials which will stabilize H under pickling conditions. Among the materials suggested have been urea (German Pat. No. 1,255,443), fatty acids (British Pat. No. 1,119,969, French Pat. No. 1,468,442, and U.S. Pat. No. 3,537,895), saturated aliphatic alcohols (French Pat. No. 1,539,960), glycerin (U.S. Pat. No. 3,345,225), certain phenols and unsaturated alcohols (U.S. Pat. No. 3,649,194), and phosphoric acid (U.S. Pat. No. 3,373,113).

SUMMARY OF THE INVENTION According to the present invention there are provided stabilizers selected from the group consisting of succinic, glutaric, and adipic acids, salts, methyl derivatives, and mixtures thereof, which stabilize against copper ion-induced degradation of H 0 in acidic oxidizing solutions at temperatures up to about 90C. The copper ions (primarily in the cupric form) may be present in concentrations of up to about 5% by weight. The stabilizers will function in any nonoxidizing mineral acid, sulfuric acid being the most commonly employed. The acid concentration may range from about 0.01 to 50% by weight, preferably about 2 to 25% by weight. The H 0 may be present in concentrations from about 0.01 to 80% by weight. These stabilizers may be formulated with H 0 and acid to form an aqueous, acidic oxidizing solution, or may preferably be included in the concentrated aqueous H 0 solution, as commercially prepared and sold, prior to adding the H 0 to the pickling bath.

DETAILED DESCRIPTION OF THE INVENTION It has now been found that copper ion-induced or catalyzed decomposition of H 0 in aqueous acidic medium at elevated temperatures can be controlled by the addition of stabilizing amounts of succinic, glutaric, or adipic acids, their mono-, di-, or trimethyl derivatives, their salts, or mixtures of them. The effectiveness of the stabilizer is greater the longer the chain length, i.e., adipic acid is the most effective and succinic acid is least effective. The stabilizers may be used in'any appropriate concentration; however, if the stabilizer is to be formulated into concentrated H 0 prior to addition to the pickling bath, the solubility of the stabilizer in concentrated H 0 may be the controlling factor. For example, the solubility of adipic acid in 35% H 0 is only about 1% by weight. In pickling baths some stabilizing effect will be seen with as little as 0.003% stabilizer concentration. The usual concentration range in pickling baths will be about 0.015 to 1.5%, preferably about 0.03 to 0.1%. Mixtures of the stabilizers may also be used. Since adipic acid is the most effective, a mixture would preferably include it, attention being paid to the solubility considerations already noted. A particularly preferred mixture is the ratio of about 2 parts of succinic acid to 1 part of adipic acid.

In commercial operations it will be found particularly convenient if the stabilizer is incorporated into the concentrated aqueous H 0 as available commercially. Such a solution can be readily formulated by the H 0 manufacturer to contain at least 0.05% and as much as 5% by weight stabilizer, depending on the solubility of the stabilizer and the concentration of the H 0 While the stabilizers of this invention will be effective in any strong, nonoxidizing mineral acid solution, sulfu ric acid is of most commercial significance. It may also be noted that Caros acid, an equilibration product of H 50 and H 0 may be present in the stabilized solution without detracting from the usefulness of the stabilizers. The H 50 concentration of a pickling bath usually is in the range of about 2 to 25% by weight, preferably 4 to 6%. Other nonoxidizing mineral acids may also be used in these concentration ranges. Such other mineral acids would include hydrochloric, hydrofluoric and phosphoric, such acids being used in the pickling of such metals as iron and aluminum and their alloys.

Hydrogen peroxide concentration in a pickling bath typically ranges from about 0.05 to 15% by weight, preferably 0.5 to 3%, although concentrations as low as 0.01% and as high as 50% may be used. If the stabilizer is formulated into concentrated aqueous H 0 the H 0 concentration may range from about 20 to by weight, preferably about 30 to 70% more preferably about 35 to 50%. While the stabilizers of this invention may be added directly to H 0 of 70% or greater concentration, this is not recommended since solubility is lessened and there is the possibility of forming peroxyacids. If it is desired to start with, say, 70% H 0 the preferred procedure would be to dissolve the stabilizer in sufficient water that when added to the 70% H 0 the overall H 0 concentration would be reduced to a more easily handled concentration, say, 50%. Even when the stabilizer is to be added to 50% or less H 0 it is still preferred to dissolve the stabilizer in water before addition to the H 0 Any commercially available grade of H 0 may be used in this invention. The H 0 may be unstabilized or preferably may contain any of the usual stabilizing chemicals, e.g., sodium stannate, sodium pyrophosphate, fluosilicates, magnesium sulfate coupled with an alkylidene diphosphonic acid (as taught by U.S. Pat. No. 3,687,627), as well as sodium nitrate and other additives. When present in concentrated commercial H 0 solutions, the concentrations in percent by weight of the more common stabilizers are as follows: stannates, 0001-1 .0%, preferably 0.015-0.07%; pyrophosphates, 0.01-5.0%, preferably 0.05-4.0%; nitrates, 0.00l0.05%, preferably 0.0015-'0.04%. An alkylidene diphosphonic acid will preferably be present in a concentration of at least 0.1% by weight.

The stabilizers of this invention will effectively control copper catalyzed decomposition of H 0 at temperatures up to about C. However, in most uses the typical temperature range would be about 15 to 40C.

EXAMPLE I I claim:

1. An aqueous, acidic, oxidizing solution stabilized against copper ion-catalyzed degradation at temperatures of up to about 90C. containing about 0.01 to 50 This example illustrates the stabilizing effect of the percent h d id b wei ht, a strong inoracids of this invention. ganic acid at a concentration of about 0.0] to 50 per- A solution having the following composition was precent by weight, and a stabilizing amount of a stabilizer d; selected from the group consisting of adipic acid, glum taric acid, succinic acid, and mixtures thereof. 2 5 2 5H 0 2. The solution of claim 1 wherein the stabilizer conj 2 z centration is about 0.003 to 1.5 percent by weight.

I 3. The solution of claim 2 wherein the stabilizer con- This solution was then d v ded and formulated with stacentration is about 0.015 to percent by weight bilizer addltlve and Stability of the 2 2 at 1200B was 15 4. The solution of claim 3 wherein the stabilizer condetermined, with the following results. Decomposition centration i about 03 to 0 percent b i h of H 0 was measured by the standard potassium per- 5. The solution of claim 1 wherein the acid concenmanganate titration test. tration is about 2 to percent by weight.

Table l Additive Residual H202, 7i

2.5 hrs. 5 hrs. 24 hrs. 70 hrs.

None (control) 85 66 6 0.5% adipic acid 100 96 7l 0.2'7: succinic acid 98 97 8] 49 0.5% succinic acid 99 98 90 49 017% adipic acid 0.33% succinic acid [00 99 95 68 EXAMPLE 2 6. The solution of claim 1 wherein the H 0 concen- Table u illustrates the effect of pH when a stabilizer 1335232352 g p t g y g gz of the invention IS added to standard commercial connation is about 5 to 3 percent by weight. Centraed H202 The H202 grades used were: 8. The solution of claim 1 wherein the stabilizer is Sample A Du Ponts Albone (regular), 35% conadipic acid centration 9. The solution of claim 1 wherein the stabilizer is Sample B Du Ponts Albone (cosmetic grade), l i id,

35% concentration 10. The solution of claim 1 wherein the stabilizer is In Samples A and B the pH of3.5 was obtained by addisuccinic acid. tion of a sodium hydroxide solution. Samples C and D The Solution f filaim 1 wherein the Stabihlef is are the same as A and B, respectively, except that no a mmure of pH adjustment was made. Sample E was the same as C l'?" of i 11 ,wherem the mmure hat the H was ad'usted b addition of H PO comprises succlmc and f except t p 3 y 3 13. The solution of claim 12 wherein the ratio of suc- A PH of about that Obtamed nrflwrany cinic acid to adipic acid is approximately 2:1 by weight. tion to 35% H 0 of about 3% ofthe acids ofthls mven- A Concentrated, aqueous acidic Solution of tion. Whereas commercial concentrated H 0 is typidrogen peroxide Stabilized against copper i Cally Sold at 3 P of about Table H Shows that it catalyzed degradation by a stabilizing amount of a stais not desirable to adjust pH to this value after addition bilizer selected from the group consisting of adipic of the acid stabilizers. Stability will be optimized by alacid, glutaric acid, succinic acid, and mixtures thereof. lowing the pH to remain at its natural level. Solution Q clflim 14 wherein the hydrogen peroxide concentration 15 about 30 to 70 percent by weight. Table ll 16. The solution of claim 15 wherein the hydrogen peroxide concentration is about 35 to 50 percent by 3% Succinic Acid in 35% H O, weight Sample PH 7! LOSS (20 hrs at 50%.. The solution of claim 14 wherein the stabilizer is adlplc acid. A 3.5 5.0 18. The solution of claim 14 wherein the stabilizer is g glutaric acid. D L5 0.6 19. The solution of claim 14 wherein the stabilizer is E 20 succinic acid.

20. The solution of claim 14 wherein the stabilizer is a mixture of the stabilizers.

A peroxide loss of about 2% or less is considered commercially satisfactory.

21. The solution of claim 20 wherein the mixture comprises succinic and adipic acids.

3,864,271 6 22. The solution of claim 21 wherein the ratio of sucthe group consisting of stannates, sulfates, pyrophoscinic acid to adipic acid is approximately 2:] by weight. phates, fluosilicates, nitrates, and alkylidene diphos- 23. The solution of claim 14 which contains in addiphonic acid. tion one or more stabilizing chemicals selected from 

2. The solution of claim 1 wherein the stabilizer concentration is about 0.003 to 1.5 percent by weight.
 3. The solution of claim 2 wherein the stabilizer concentration is about 0.015 to 1.5 percent by weight.
 4. THE SOLUTION OF CLAIM 3 WHEREIN THE STABILIZER CONCENTRATION IS ABOUT 0.03 TO 0.1 PERCENT BY WEIGHT.
 5. The solution of claim 1 wherein the acid concentration is about 2 to 25 percent by weight.
 6. The solution of claim 1 wherein the H2O2 concentration is about 0.05 to 15 percent by weight.
 7. The solution of claim 6 wherein the H2O2 concentration is about 0.5 to 3.0 percent by weight.
 8. The solution of claim 1 wherein the stabilizer is adipic acid.
 9. The solution of claim 1 wherein the stabilizer is glutaric acid.
 10. The solution of claim 1 wherein the stabilizer is succinic acid.
 11. The solution of claim 1 wherein the stabilizer is a mixture of the stabilizers.
 12. The solution of claim 11 wherein the mixture comprises succinic and adipic acids.
 13. The solution of claim 12 wherein the ratio of succinic acid to adipic acid is approximately 2:1 by weight.
 14. A concentrated, aqueous, acidic solution of hydrogen peroxide stabilized against copper ion-catalyzed degradation by a stabilizing amount of a stabilizer selected from the group consisting of adipic acid, glutaric acid, succinic acid, and mixtures thereof.
 15. The solution of claim 14 wherein the hydrogen peroxide concentration is about 30 to 70 percent by weight.
 16. The solution of claim 15 wherein the hydrogen peroxide concentration is about 35 to 50 percent by weight.
 17. The solution of claim 14 wherein the stabilizer is adipic acid.
 18. The solution of claim 14 wherein the stabilizer is glutaric acid.
 19. The solution of claim 14 wherein the stabilizer is succinic acid.
 20. The solution of claim 14 wherein the stabilizer is a mixture of the stabilizers.
 21. The solution of claim 20 wherein the mixture comprises succinic and adipic acids.
 22. The solution of claim 21 wherein the ratio of succinic acid to adipic acid is approximately 2:1 by weight.
 23. The solution of claim 14 which contains in addition one or more stabilizing chemicals selected from the group consisting of stannates, sulfates, pyrophosphates, fluosilicates, nitrates, and alkylidene diphosphonic acid. 